Sewing machines have been conventionally provided with a presser foot for pressing a workpiece cloth against a sewing machine bed. The presser foot is typically attached to a lower end of a presser bar which is vertically movably supported by a head provided at the extremity of a sewing machine arm. Under such configuration, a presser foot lifting unit provided with a presser foot lifting lever for lifting the presser foot is generally provided within the head. The presser foot lifting unit is configured to vertically move the presser bar and the presser foot by manual rotation of the presser foot lifting lever by the user.
Some sewing machines are provided with a knee lever instead of a manually operated presser foot lifting lever to allow the user to vertically move the presser foot by operation of the knee lever with his/her knees. Such types of sewing machines are provided, at the sewing machine bed (or sewing machine table), components such as a knee lever attachment (hereinafter referred to as an attachment), an operative shaft rotating integrally with the attachment and a link mechanism providing linkage between the operative shaft and the presser foot. Under such configuration, when the knee lever is laterally moved by user operation, the attachment and the operative shaft are rotated to vertically move the presser foot through the link mechanism.
One example of such sewing machine is disclosed, for example, in JP S62-15029 Y hereinafter referred to as patent publication 1 in which a guide mechanism is provided between the attachment and the operative shaft. The guide mechanism is provided with a guide member including a guide cam and being secured on the sewing machine table and a swing arm provided on the operative shaft. The guide mechanism is configured to guide the attachment and consequently the knee lever through engagement of a pair of pins disposed at a lower portion of the attachment with the guide cam and the swing arm. The knee lever, on the other hand, is provided with a rod secured on the attachment and a knee rest provided on the rod. The rod comprises a vertical section and a horizontal section and is generally curved in an “L-shape”. The horizontal section is secured to the attachment by a screw serving as a fastening element. In the disclosed sewing machine, when the user laterally moves his/her knees to laterally operate the knee rest, the guide mechanism guides the knee rest so that the path of its movement follows the user knee movement. Such guidance feature allows smooth and stress free knee operation of the knee lever.
Another example is disclosed in JP H11-207066 A, hereinafter referred to as patent publication 2. Patent publication 2 discloses a presser lifting unit allowing detachable attachment of knee lever to provide the user with an option to control the vertical movement of the presser foot with the knee lever.
The problem encountered in the knee lever operation disclosed in patent publication 1 was the variability in the requirement in the positioning of the knee rest depending upon the physiques of the user. For instance, some users may feel that the knee rest is too far away whereas some may feel that it is too close for stress free operation. In such case, the user is forced to go through a troublesome task of knee lever adjustment involving unfastening of the screw with special tools such as a wrench, then, laterally moving the horizontal section of the rod to reposition the knee lever in its entirety, and fastening the screw again with the tool. The guide mechanism mentioned earlier for providing guidance during the knee lever operation is disposed on the sewing machine by screw fastening as was the case for the attachment. Such configuration also complicated the structure of the sewing machine.
The knee lever disclosed in patent publication 2 does not allow adjustment in its positioning relative to the sewing machine, and thus, provided poor operability if its positioning did not suit the physiques of the user.